Module `_operations`: replace `factories.array()` with `DNDarray` construct where possible

[ClaudiaComito]

Feature functionality
Will result in significant performance enhancement. Probably requires expanding the tests.

[ClaudiaComito]

Update:

the ht.array() calls that might significantly affect runtime and memory footprint as those where is_split is specified. When is_split is not None, ht.array() results in several MPI collective operations which require synchronization among processes (=waiting time) and communication of buffers (increased memory footprint). Especially if the compute load is imbalanced, this might potentially result in a lot of waiting.

As of Aug 2023 there is exactly one instance of ht.array(is_split) in the _operations module, in _operations.__cum_op(). Global shape of the result can be easily calculated via DNDarray.__torch_proxy__.

This issue is still open, not the highest priority but an easy enough fix.

[github-actions]

Branch 804-Module__operations_replace_factories_array_with_DNDarray_construct_where_possible created!